Potential Grazing Land Within the Pacific Drainages of the Western United States

The U.S. Geological Survey (USGS) is developing SPARROW models (SPAtially Related Regressions On Watershed Attributes) to assess the transport of contaminants (e.g., sediment and nutrients) through United States Pacific watersheds (the Columbia River basin; the coastal drainages of Washington, Oregon, and California; the Klamath River basin; the Central Valley of California, and the west slopes of the Sierra Nevada Mountains). SPARROW relates instream water quality measurements to spatially referenced characteristics of watersheds, including contaminant sources and factors influencing terrestrial and aquatic transport. A watershed property that is expected to influence sediment and nutrient delivery to streams is the area of potential livestock grazing land. The spatial data set "Potential Grazing Land Within the Pacific Drainages of the Western United States, 2011" represents areas that were suitable for livestock grazing (primarily cattle) in 2011. This data set was developed by considering relevant landscape attributes with regards to the potential for land to be suitable for livestock grazing. These attributes included land cover type, slope, proximity to water bodies and streams and designated grazing allotments.

The purpose of this data set is to provide water-quality and land management analysts with a tool for assessing the importance of livestock grazing in the Pacific watersheds of the United States. The existing data sets representing potential grazing land within the Pacific watersheds are inadequate. One dataset that was developed for the Pacific Northwest region (Wise, D.R., Johnson, H.M., 2013) used a similar approach as the one used to compile to the data set described here, but was for 2001 conditions and, more importantly, does not include the Klamath River Basin in Oregon or any of the watersheds in California. Another dataset that was developed for the entire United States (Falcone, J.A., 2015) does not include large areas of shrub, scrub and forest land that comprise a substantial portion of the potential grazing land in the Western United States. The new dataset representing potential grazing land in 2011 could be useful in watershed modeling, as well as other types of water-quality and land management analyses in the western United States. References Cited: Wise, D.R., and Johnson, H.M., 2013, Application of the SPARROW model to assess surface-water nutrient conditions and sources in the United States Pacific Northwest: U.S. Geological Survey Scientific Investigations Report 2013–5103, 32 p., Falcone, J.A., 2015, U.S. conterminous wall-to-wall anthropogenic land use trends (NWALT), 1974–2012: U.S. Geological Survey Data Series 948, 33 p. plus appendixes 3–6 as separate files,